Data from: Postglacial expansion pathways of red mangrove, Rhizophora mangle, in the Caribbean Basin and Florida

PREMISE OF THE STUDY: The Last Glacial Maximum (LGM) was a period of massive range contraction. Post-LGM, water-dispersed coastal species, including the red mangrove (Rhizophora mangle), expanded poleward as propagules were transported by ocean currents. We assessed postglacial marine expansion pathways for R. mangle within the Caribbean Basin and Florida. METHODS: Six microsatellite loci were used to genotype 237 individuals from nine R. mangle populations in the Caribbean, Florida, and Northwest Africa. We evaluated genetic variation, population structure, gene flow along alternative post-LGM expansion pathways to Florida, and potential long-distance dispersal (LDD) from West Africa to Caribbean islands. KEY RESULTS: These R. mangle populations had substantial genetic structure (FST = 0.37, P < 0.0001) with three discrete population clusters (Caribbean mainland, Caribbean islands, and Florida). Genetic connectivity along the mainland pathway (Caribbean mainland to Florida) vs. limited gene dispersal along the Antilles Island pathway (Caribbean islands to Florida) supported Florida recolonization from Caribbean mainland sources. Genetic similarity of Northwest Africa and two Caribbean islands provided evidence for trans-Atlantic LDD. We did not find a pattern of decreasing genetic diversity with latitude. CONCLUSIONS: We outline a complex expansion history for R. mangle, with discrete pathways of recolonization for Florida and Caribbean islands. Contrary to expectation, connectivity to putative Caribbean mainland refugial populations via ocean currents, and not latitude, appears to dictate genetic diversity within Caribbean island and Florida R. mangle. These findings provide a framework for further investigation of additional water-dispersed neotropical species, and insights for management initiatives.

研究背景：
末次冰盛期（Last Glacial Maximum, LGM）是物种分布范围大幅收缩的地质时期。末次冰盛期结束后，以红树（Rhizophora mangle）为代表的水传播海岸物种，其繁殖体借助洋流完成运输，随之向极地方向扩张分布范围。本研究针对加勒比海盆与佛罗里达地区的红树（R. mangle），评估了其冰期后的海洋扩张路径。
研究方法：
本研究利用6个微卫星位点（microsatellite loci），对取自加勒比海、佛罗里达与西北非的9个红树种群的237个个体进行基因分型。我们对遗传变异水平、种群遗传结构、沿多条通往佛罗里达的冰期后备选扩张路径的基因流情况，以及从西非到加勒比群岛的潜在长距离扩散（long-distance dispersal, LDD）事件进行了分析评估。
主要结果：
本次研究涉及的红树种群存在显著的遗传结构分化（FST = 0.37, P < 0.0001），可划分为3个独立的种群簇：加勒比大陆种群、加勒比群岛种群与佛罗里达种群。沿大陆路径（加勒比大陆至佛罗里达）的遗传连通性较强，而安的列斯群岛路径（加勒比群岛至佛罗里达）的基因扩散较为有限，该结果支持佛罗里达种群的重新定殖源自加勒比大陆避难所种群。西北非种群与两个加勒比群岛种群之间的遗传相似性，为跨大西洋长距离扩散提供了实证依据。本研究未观测到遗传多样性随纬度降低的分布模式。
研究结论：
本研究阐明了红树物种复杂的扩张历史，佛罗里达种群与加勒比群岛种群拥有各自独立的重新定殖路径。与传统预期相悖的是，洋流介导的与加勒比大陆避难所种群的遗传连通性（而非纬度因素），似乎才是决定加勒比群岛与佛罗里达红树种群遗传多样性水平的关键因素。本研究结果可为后续探究其他水传播新热带物种提供研究框架，同时可为相关海洋海岸物种的保护管理举措提供科学参考。